1. Field of the Invention
The present invention relates to a head for checking dimensions of mechanical parts including feeling devices adapted to contact the part to be checked; an integral member defining a support portion, a plurality of movable supports for the feeling devices, and a plurality of portions having a lightened section for permitting rotational movements of the feeling devices with respect to the support portion; and detecting devices for generating signals responsive to said movements. The present invention has particular applicability to snap gauges for checking a plurality of diameters.
2. Description of the Prior Art.
From U.S. Pat. No. 4,409,737, devices, or measuring cells are known that basically comprise an integral element with a first portion, a second portion--movable with respect to the first portion--carrying a feeler, and a third portion that couples the first portion to the second portion and permits the movement of the second portion. The device also comprises transducer means that transform the feeler movements into electrical signals.
Cells of this type can be used for simultaneous measurements of several dimensions, for applications in measuring benches, or in other types of apparatuses.
For example a known gauge, of the type called "snap" gauge, that is used for checking radial dimensions of shafts, substantially comprises an element for positioning and supporting the part to be checked and a support onto which are fixed six measuring cells, arranged three by three side by side and in diametrally opposite positions with respect to the part axis. Since diametral dimensions of the same shaft have to be checked, it is important that the position of the measuring devices be very accurate. Therefore, the three cells arranged side by side must permit rotational displacements of the relevant feelers about axes that should be exactly parallel, or rather, coinciding. Consequently, it is understood that the operation for assembling the gauge requires high skill and care and involves a considerable amount of time.
In the prior art it has been suggested to make measuring devices, or similar devices, comprising an integral member defining a plurality of fulcrums for a measuring arm. For example, British patent application No. 2129133 shows a contact-detecting head with an integral member having a first portion carrying a movable arm, a second portion secured to a support, at least a third intermediate portion and portions having a reduced thickness that connect the first and second portion to the third portion, while defining rotation axes for mutual displacements of the different portions. The movable arm carries a feeler that moves together with the arm itself and switching elements are arranged between the portions for detecting the arm movement caused by the contact of the feeler against a part to be checked. The particular structure of the integral member permits movements of the feeler along at least two directions. However, the operation and purpose of the device described in British patent application No. 2129133 are completely different from the operation and purpose of the present invention.